After brawling over a card game in the wharf area of New Orleans, a man named Kochak (Lewis Charles), suffering visibly from a flu-like illness, is killed by gangster Blackie (Jack Palance) and his two flunkies, Kochak's cousin Poldi (Guy Thomajan) and a man named Fitch (Zero Mostel). They leave the body on the docks, and later when the dead man, who carries no identification, is brought to the morgue, the coroner grows suspicious about the bacteria present in his blood and calls Lieutenant Commander Clinton Reed (Richard Widmark), a doctor working for the U.S. Public Health Service. Reed is enjoying a rare day off with his wife Nancy (Barbara Bel Geddes) and their son Tommy (Tommy Rettig), but decides to inspect the body.